Antibody against tuberlin: the specific visualization of cytoplasmic microtubules in tissue culture cells

In vitro complement binding on cytoplasmic structures in normal human skin: immunoelectronmicroscopic studies

We have previously provided evidence that suggests that exposure of cryostat skin sections to normal human serum (NHS) results in the antibody-independent Clq binding to cytoplasmic structures of various cell types, leading to classical complement pathway activation as evidenced by cytoplasmic C3 deposition. In the present study, we have employed immunoelectronmicroscopic methods to clarify the exact nature of cytoplasmic C3 binding structures. Incubation of cryostat skin sections with NHS followed by peroxidase-labeled rabbit anti-human C3 serum (HRP-R/Hu C3) revealed that intracytoplasmic binding of C3 occurred in suprabasal keratinocytes, melanocytes, fibroblasts, smooth muscle cells, endothelial cells, pericytes, Schwann cells, and nerve axons, but not in basal keratinocytes, Langerhans cells, and other cellular constituents of the skin. C3 binding, as revealed by the deposition of HRP reaction product, was exclusively confined to intermediate-sized filaments (ISF), which can therefore be considered to represent the subcellular site for classical complement pathway activation. Under experimental conditions that do not allow classical complement pathway activation, ISF were not decorated. Our observation that ISF of ontogenetically different cell types share the capacity of complement fixation is in accordance with the recent finding that different ISF types, despite their biochemical and antigenic heterogeneity, have common alpha-helical domains and may provide a clue to the mechanism and site of interaction between complement components and ISF.

Extraction and immunochemical assays of a tubulin-like factor in cotton seedlings

Antibodies to tubulin were prepared in rabbits by immunization with reduced-carboxymethylated calf-brain tubulin. In immunodiffusion tests the antibodies showed full cross reactivity with the immunogen as well as with native calf-brain tubulin. The same antibodies showed cross reactivity with a factor in extract of cotton (Gossypium hirsutum L.) cotyledons but there was no full immunological identity between calf-brain tubulin and this factor. A solid-phase radioimmunoassay for quantitative estimation of this plant tubulin-like factor was developed. It measured the binding of antibodies to immobilized calf-native tubulin. Competition between the unknown soluble tubulin-like factor, and immobilized tubulin was assayed at serum dilution of 1:50. Extraction conditions which preserved the antigenic properties of the tubulin-like factor from cotton cotyledons were defined. The radioimmunoassay measured quantities of the tubulin-like factor in the range of 0.1-10 μg-equivalents of calf-brain tubulin. Immediately after homogenization of the tissue only 25% of the total amount of tubulin-like activity was present in soluble form, while most of it remained in the insoluble fraction. Apparent maximal solubilization was achieved spontaneously 10 h after homogenization or by treatment with guanidine hydrochloride. These results indicate that in this material, tubulin is not released immediately by homogenization but remains assembled in microtubules and-or in a bound or sequestered form.

In vitro biosynthesis of mouse hair keratins under the direction of follicular RNA

A hair follicle-enriched fraction from neonatal C57BL/6J mouse skin has been obtained by a newly-developed preparative procedure. RNA isolated from this source directs protein synthesis in a cell-free translation system derived from rabbit reticulocytes. Translation products in the molecular weight range of keratins (45,000-70,000 Mr) are encoded by RNA species which sediment at 18S on sucrose density gradients. Proteins of 63K, 59K, 58K, 47K and 46K Mr were identified as keratins on the basis of electrophoretic mobilities identical with authentic hair keratins and by immunoprecipitation with keratin antiserum.

Microtubular organization in flat epitheloid and stellate process-bearing astrocytes in culture

Microtubules and microfilament patterns in cultured astrocytes were revealed by using indirect immunofluorescent microscopy in conjunction with anti-tubulin immune serum and anti-actin immunoglobulins respectively. In flat epitheloid astroglial cells (either polygonal or elongated) colchicine-sensitive immunofluorescent fibres, which correspond to bundles of microtubules, extend from the perinuclear cytoplasm into the cell periphery by running for long distances through the different focal planes. These patterns of organization differ markedly from the patterns of organization of microfilaments which are arranged in fibres parallel to each other and often oriented along the cell boundary. In response to the combined treatments of serum withdrawal and administration of dBcAMP, flat epitheloid astrocytes adopt a morphology similar to that of the mature astrocytes in situ in the CNS, that is of stellate process-bearing cells. This is prevented or is reverted by the administration of colchicine at the appropriate times. There are strong suggestions indicating that during cell processes formation the microtubular network is reorganized and microtubules assembled into dense bundles which are oriented along the axis of the cell processes. In view of these results, we suggest that, in contrast to microfilaments, microtubules are not determinant for the maintenance of cellular shape in elongated or polygonal flat epitheloid astroglial cells but they are required for both the formation and maintenance of processes in stellate astrocytes.

Visualization of microtubules in interphase and mitotic plant cells of Haemanthus endosperm with the immuno-gold staining method

A procedure is presented for the immunocytochemical visualization of microtubules in interphase and mitotic cells of Haemanthus endosperm. It includes preservation of microtubules (MTs) with glutaraldehyde and uses colloidal gold, coated with secondary antibodies, in a novel indirect-light microscopic technique: the immuno-gold staining method. This immunocytochemical stain allows us to follow the changes in distribution of MTs during mitosis with greater precision and specificity than allowed by other light microscopic techniques. Many aspects of MT arrangements, as reported from ultrastructural studies, are corroborated and extended. This demonstrates the reliability of the technique. In addition, a number of significant observations were made. These concern (i) the presence of a network of MTs in interphase cells, (ii) the transformation of this network into a spindle-like cage of MTs (the clear zone) surrounding the nucleus during prophase, (iii) the drastic rearrangement of MT distribution during prometaphase, (iv) new evidence for the formation of aster-like arrays of polar MTs during anaphase, and (v) the development of the phragmoplast.

Fate of secretory proteins trapped in oocytes of Xenopus laevis by disruption of the cytoskeleton or by imbalanced subunit synthesis

The effects of imbalanced subunit synthesis, temperature, colchicine, and cytochalasin on the secretion from Xenopus laevis oocytes of a variety of avian and mammalian proteins were investigated; these proteins were encoded by microinjected messenger RNA. Cytochalasin and colchicine together severely reduced secretion in a temperature-independent manner, the exact reduction varying among the different proteins. In contrast cytochalasin alone had no effect, whereas colchicine alone caused a smaller, temperature-dependent reduction. The synthesis and subcellular compartmentation of these proteins were unaffected by the drug treatments; however, the proteins did not accumulate in the drug-treated oocytes but were degraded. The rate of degradation of each protein was similar to its rate of exocytosis from untreated oocytes. A similar result was obtained without recourse to drugs by studying the fate of immunoglobulin light chains trapped in oocytes by a deficiency in heavy chain synthesis. These results are discussed in terms of the disruptive effects, as revealed by electron microscopy, of the drug treatments on the cytoskeleton of the oocyte.

Microtubules and microfilaments during cell spreading and colony formation in PK 15 epithelial cells

We have studied the distribution of microtubules and microfilaments during the cell spreading and subsequent colony formation in PK 15 pig kidney epithelial cells using indirect immunofluorescence. During the cell spreading on a solid substratum, microtubules grew out from the region around the nucleus, and a collar of microfilament bundles formed around the cell periphery. Although virtually all well-spread cells showed a complex microtubular network, distinctly different patterns of stress fibers were observed. In small colonies, the most commonly observed pattern was a ring of microfilament bundles that appeared to be in register between adjacent cells and encircled the entire colony in a fashion similar to that seen in single cells. In large colonies (more than 50 cells), approximately 60% of the cells displayed clearly stained microfilament bundles, either at the cell periphery or throughout their cytoplasm, whereas in the remaining 40%, no microfilament bundles were observed and only the outline of the cells was delineated by interaction with anti-actin. Such "negative" cells were seen in groups alongside "positive" cells (i.e., cells possessing extensive stress fiber networks) within the same colony. Independent of their stress fiber phenotype, all cells maintained a flattened shape and an extensive network of microtubules. We suggest that dense microfilament bundles are not a uniform feature of well-spread PI 15 cells in culture and that a loss of microfilament bundle occurs in some cells.

Immunocytochemical study of microtubules in chromaffin cells in culture and evidence that tubulin is not an integral protein of the chromaffin granule membrane

Bovine adrenal chromaffin cells were maintained in culture in Dulbecco's modified Eagle's medium containing 20% foetal calf serum and 10 units per ml of Nerve Growth Factor. Under these conditions, chromaffin cells developed up to five neurites per cell. The neurites showed lateral branches and varicosities along their trunk which ended with thick growth cone-like structures. Cultures of chromaffin cells were stained by indirect immunofluorescence with antibodies against (a) chromogranin A to follow the distribution of chromaffin granules, the catecholamine-storing organelles, and (b) tubulin, to study the microtubular system during outgrowth of neurites. Chromogranin A antibodies showed a very intensely staining punctate pattern, not randomly distributed but localized in neurites. Chromaffin granules were found to migrate from the cell body to reach neurite endings where they were densely packed. Intense staining was also observed in varicosities; a linear arrangement of granules was evident along neurite trunks. Tubulin antibodies decorated a complex network, clearly visible at the cell periphery and also in the growth cone-like structures, in the palm region of the growth cone. Colchicine treatment effected retraction of neurites and disappearance of organized microtubule networks; chromaffin granules were found in the perinuclear region of the cell. Some tubulin (0.2% of total membrane proteins) was found in the purified chromaffin granule membrane preparation; however, this tubulin is probably associated with contaminating plasma membranes. By the criteria of morphology and staining with antitubulin antibodies, adult bovine chromaffin cells in culture display characteristics similar to those of sympathetic neurones. In addition, they showed an exaggerated transport of granules. Adult bovine chromaffin cells in culture offer an excellent model for studying the role of microtubules and the contractile apparatus in relation to cell morphological changes and neurosecretion.

Immunocytochemical studies of neurofibrillary tangles

The molecular nature of neurofibrillary tangles of senile dementia of the Alzheimer type (SDAT) was studied by immunoperoxidase and immunofluorescence techniques. Five antiserums, including anti-humanbrain-2-cycle-purified-microtubule-fractions (2 x MT), anti-calf-brain-2 x MT, anti-sea-urchin-egg-tubulin, antibeef-brain-tubulin, and anti-human-brain-neurofilament(NF)-210-kilodalton(kd)-protein were tested for their binding to neurofibrillary tangles. The antihuman-2 x MT serum stained structures resembling neurofibrillary tangles, neurites of neuritic plaques, and microglialike cells in SDAT brains, but no such staining pattern was detected in normal brain sections. In neurons isolated from SDAT brains, about 40% of the tangles were labeled by the anti-human-2xMT serum with an identical pattern. Other antiserums tested did not preferentially bind tanglelike structures in tissue sections and bound to less than 5% of the tangles in isolated neurons. These results suggest that the antigenic sites of tubulin and NF proteins are not shared by neurofibrillary tangles. Different from the calf preparation, the human-2 x MT fractions contained a prominent protein band that was identical to ferritin in molecular weight and cross-reacted with anti-human-2 x MT and anti-human-ferritin serums. However, antiserums to this ferritinlike protein, or anti-ferritin, did not stain neurofibrillary tangles. Although neither the calf 2 x MT nor two other human MT fractions failed to elicit an antiserum that stained tangles, these fractions were able to remove the antihuman-2 x MT serum activity that binds to tangles. The data suggest that the protein (or proteins) that makes up neurofibrillary tangles of SDAT is present in various quantities in microtubule fractions of normal brain.

ATP-dependent regulation of cytoplasmic microtubule disassembly

Indirect immunofluorescent staining with an antitubulin antibody was used for studying the role of ATP in the regulation of cytoplasmic microtubule disassembly. Depletion of the cellular ATP pool in cultured mouse fibroblasts with various inhibitors of energy metabolism leads to inhibition of the microtubule disassembly induced by colcemid or vinblastine. Glucose added to the inhibitor-containing incubation medium partially restores the cellular ATP content and abolishes the inhibition of microtubule disassembly. The metabolic inhibitors did not change [3H]colcemid uptake by the cells; therefore, their action on the microtubule disassembly was not caused by the reduction in intracellular colcemid. Addition of ATP to the cytoskeleton preparations obtained by Triton X-100 treatment of the cells markedly stimulates microtubule depolymerization. This effect was specific for ATP; it was not observed in the presence of GTP, UTP, CTP, ADP, AMP, adenosine 5'-(beta, gamma-methylene)triphosphate (a nonhydrolyzable analogue of ATP), or inorganic pyrophosphate or tripolyphosphate. Therefore, depletion of the cellular ATP pool reduces the rate of microtubule disassembly whereas addition of ATP increases it. These results suggest that a certain ATP-dependent reaction [most probably, phosphorylation of some of the microtubule protein(s)] controls microtubule disassembly in the cells.

Organization of pp60src and selected cytoskeletal proteins within adhesion plaques and junctions of Rous sarcoma virus-transformed rat cells

The localization of pp60src within adhesion structures of epithelioid rat kidney cells transformed by the Schmidt-Ruppin strain of Rous sarcoma virus was compared to the organization of actin, alpha-actinin, vinculin (a 130,000-dalton protein), tubulin, and the 58,000-dalton intermediate filament protein. The adhesion structures included both adhesion plaques and previously uncharacterized adhesive regions formed at cell-cell junctions. We have termed these latter structures "adhesion junctions." Both adhesion plaques and adhesion junctions were identified by interference-reflection microscopy and compared to the location of pp60src and the various cytoskeletal proteins by double fluorescence. The results demonstrated that the src gene product was found within both adhesion plaques and the adhesion junctions. In addition, actin, alpha-actinin, and vinculin were also localized within the same pp60src-containing adhesion structures. In contrast, tubulin and the 58,000-dalton intermediate filament protein were not associated with either adhesion plaques or adhesion junctions. Both adhesion plaques and adhesion junctions were isolated as substratum-bound structures and characterized by scanning electron microscopy. Immunofluorescence revealed that pp60src, actin, alpha-actinin, and vinculin were organized within specific regions of the adhesion junctions. Heavy accumulations of actin and alpha-actinin were found on both sides of the junctions with a narrow gap of unstained material at the midline, whereas pp60src stain was more intense in this central region. Antibody to vinculin stained double narrow lines defining the periphery of the junctional complexes but was excluded from the intervening region. In addition, the distribution of vinculin relative to pp60src within adhesion plaques suggested an inverse relationship between the presence of these two proteins. Overall, these results establish a close link between the src gene product and components of the cytoskeleton and implicate the adhesion plaques and adhesion junctions in the mechanism of Rous sarcoma virus-induced transformation.

Distribution of tubulin and actin in neurites and growth cones of differentiating nerve cells

Embryonic chick nerve cells, from dissociated dorsal root ganglia, were cultured on polylysine substrata and examined for tubulin and actin distribution by indirect immunofluorescence. Antibodies generated against chick brain tubulin produced specific fluorescence in growth cones, neurites, and cell bodies without revealing distribution differences or substructure in the nerve cells. However, at reduced antitubulin concentrations, differences were resolved. Tubulin fluorescence remained uniform and intense in neurites and cell bodies, but exhibited reduced intensity and patterning in growth cones. Nonneuronal cells in the cultures served as controls for typical cytoplasmic tubulin fluorescence distribution. Straining controls demonstrated that fluorescence resulted from tubulin-antitubulin binding. Analogous studies, using antibodies generated against chick brain actin, demonstrated distribution differences at reduced antiactin concentrations, including "hot spots" of intense fluorescence in growth cones and a paucity of fluorescence in neurites.

Pre-embedding immunohistochemistry as an approach to high resolution antigen localization at the light microscopic level

Pre-embedding immunohistochemistry with subsequent embedding in hydroxypropyl methacrylate enables one to obtain high resolution staining of antigens in 1 mu tissue sections. A routine method using formaldehyde fixation, methanol permeation, and an indirect method with fluorescein-labeled second antibody is described. This method is compared with other pre-embedding staining procedures. To illustrate the method the mouse small intestine was chosen as a model and stained with antibodies to tubulin, actin, and fibronectin. Some anticipated and some unusual staining patterns were found.

Visualization of microtubules of cells in situ by indirect immunofluorescence

Microtubule staining patterns can be visualized within cells in situ on the surface of fish scales from the squirrel fish, Holocentrus ascensionis, and the common goldfish, Carassius auratus, after incubation with antibodies to sea urchin tubulin and fluorescein-labeled goat antibodies to rabbit immunoglobulin G. Chromatophores in situ from both species reveal a radial microtubule framework that orients the alignment of pigment granules. Innervating fibers of erythrophores on the H. ascensionis scale can also be observed. In situ, pseudo-epithelial cells called scleroblasts show microtubule patterns with a remarkable degree of similarity within a selected region. Over 90% of the cells have a microtubule framework that is nearly superimposable from cell to adjacent cell. The microtubules in scleroblasts are few and form a simple radial framework with a localized microtubule organizing center (MTOC). Microtubules in scleroblasts in vitro emanate from localized MTOCs but are much less radially organized than in situ. Scleroblasts in situ on the scale of C. auratus show microtubules that curve abruptly into coalignment with phase striations on the fibrillary plate. The phase striations arise from the orthogonal plies of collagen in intimate association with the scleroblasts. The role of microtubules in scleroblasts may thus be to provide orientation for collagen fibrillogenesis, analogous to their role in orientation of cellulose fibers in plants. That cells in situ exhibit highly related and coordinated microtubule staining patterns reaffirms that the cytoskeleton plays an important role in the organization of differentiated tissues.

Effects of antibodies against tubulin on the movement of reactivated sea urchin sperm flagella

Antibodies binding to sea urchin flagellar outer-doublet tubulin have been isolated from rabbit sera by tubulin-affinity chromatography employing electrophoretically purified tubulin as the immobilized substrate. This procedure provides "induced" antitubulin antibody from immune sera and "spontaneous" antitubulin antibody from preimmune sera. These antitubulins were characterized in terms of their specificity, ability to bind to sea urchin axonemes, and effects on the motility of reactivated spermatozoa. Induced antitubulin antibody specifically reduced the bend angle and symmetry of the movement of demembranated reactivated spermatozoa without affecting the beat frequency. At identical concentrations, spontaneous antitubulin had no effect on motility. Affinity-purified induced antitubulins from three other rabbits all gave specific bend-angle inhibition, whereas their corresponding spontaneous antitubulins had no effect on the flagellar movement. The effects of antitubulin on microtubule sliding were examined by observing the sliding disintegration of elastase-digested axonemes induced by MgATP2+-. Affinity-purified induced antitubulin antibody, in quantities sufficient to completely paralyze reactivated flagella, did not inhibit microtubule sliding. The amplitude-inhibiting effect of induced antitubulin on reactivated spermatozoa may be caused by action on a mechanism responsible for controlling flagellar bending rather than by interference with the active sliding process. This is the first report of an antitubulin antibody having an inhibitory activity on microtubule-associated movement.

Variant endothelial cells. Fibronectin as a transducer of signals for migration and neovascularisation

A morphologic and growth control variant of bovine aortal endothelial cells has been isolated and shown to synthesise factor VIII antigen (McAuslan and Reilly '79). The variant also possesses the endothelial surface markers angiotensin converting enzyme and alpha 2-microglobulin. The normal cell synthesises fibronectin and deposits it underneath the cells; the variant also synthesises fibronectin. At least three times more fibronectin is distributed over the upper cell surface of variants. This correlates with the three-fold increased binding of the replication inhibitor Con A and suggests a role of fibronectin in endothelial cell growth control. When stimulated to migrate by CuII ions, the variant leaves deposits of fibronectin in its trail; in contrast, migrating normal cells do not, but they do redistribute their surface fibronectin. As revealed by scanning electron microscopy, variant cells are unusual in that they grow over or under cultured normal endothelial cells. It is proposed that during the process of neovascularisation, variant cells have a special function as lead cells that lay down fibronectin on which an endothelium can become established.

Association of microtubules and intermediate filaments in chicken gizzard cells as detected by double immunofluorescence

By double indirect immunofluorescence, using guinea pig and rabbit antibodies to tubulin and to desmin, we have simultaneously labeled microtubules and intermediate filaments in cultured chicken embryo gizzard cells. At the resolution of the light microscope there was extensive but not complete superposition of the labeling patterns for the two filamentous structures within cells in interphase and an essentially complete dissociation of the two labeling patterns in cells in mitosis. These results indicate that there is an extensive association of microtubules and intermediate filaments in these interphase muscle cells and suggest that this association is regulated metabolically.

Implications of treadmilling for the stability and polarity of actin and tubulin polymers in vivo

In this report, we examine how the cell can selectively stabilize anchored filaments and suppress spontaneous filament assembly. Because microtubules and actin filaments have an organized distribution in cells, the cell must have a mechanism for suppressing spontaneous and random polymerization. Though the mechanism for suppressing spontaneous polymerization is unknown, an unusual property of these filaments has been demonstrated recently, i.e., under steady-stae conditions, in vitro actin filaments and microtubules can exhibit a flux of subunits through the polymers called "treadmilling." In vivo, however, most, if not all, of these polymers are attached at one end to specific structures and treadmilling should not occur. The function of treadmilling in vivo is, therefore, unclear at present. However, as shown here, the same physicochemical property of coupling assembly to ATP or GTP hydrolysis that leads to treadmilling in vitro can act to selectively stabilize anchored polymers in vivo. I show here that the theory of treadmilling implies that the concentration of subunits necessary for assembly of the nonanchored polymer will in general be higher than the concentration necessary for the assembly of polymers anchored with a specific polarity. This disparity in the monomer concentrations required for assembly can lead to a selective stabilization of anchored polymers and complete suppression of spontaneous polymerization at apparent equilibrium in vivo. It is possible, therefore, that the phenomenon of treadmilling is an in vitro manifestation of a mechanism designed to use ATP or GTP hydrolysis to control the spatial organization of filaments in the cell.

Association of creatine phosphokinase with the cytoskeleton of cultured mammalian cells

Using an antibody specific for creatine phosphokinase (CPK), we have discovered an association between that enzyme and the cytoskeleton. Immunofluorescence observations show that CPK is associated with intermediate filaments in PTK cells and BALB/3T3 cells. The CPK distribution also follows intermediate filaments when cells are treated with colchicine.

Immunohistochemical and immunocytochemical localization of myosin, chromogranin A and dopamine-beta-hydroxylase in nerve cells in culture and in adrenal glands

Dopamine-beta-hydroxylase, chromogranin A and myosin were purified from bovine adrenal medulla and antibodies prepared against these proteins. Indirect immunocytochemical methods were used to localize dopamine-beta-hydroxylase, chromogranin A and myosin in bovine adrenal medulla and myosin in rat adrenal glands and cells from rat C.N.S. maintained in primary culture. Dopamine-beta-hydroxylase and chromogranin A were found in chromaffin granules, in agreement with biochemical data and, using electron microscopy, dopamine-beta-hydroxylase was found within the matrix and in the surrounding membrane of the storage granule, whereas chromogranin A was confined to the granule matrix. Myosin was localized in the vascular system irrigating adrenal glands, fibroblasts lining the vessels and chromaffin cells. In chromaffin cells, staining was found at the cell boundaries and electron microscopy showed myosin to be associated with the plasma membrane. Faint immunocytochemical staining by antimyosin antibodies was observed around certain exocytotic profiles but particular association with such structures was not demonstrable. Myosin localization was also studied in bovine adrenal cortex, where it was found in vascular channels and faintly in adrenal cortical cells, as in rat adrenal cortex and medulla, where identical patterns were obtained. In neuronal and glial cells dissociated from 13 day rat embryo cerebral hemispheres and cultured for 48 h, localization of myosin was studied using immunohistochemistry. The neuritic expansions and growth cones of neurons were fluorescent, whereas in glial cells, filamentous networks were visualized enclosing the nucleus and as long fibres traversing the entire cytoplasm.

Taxol stabilizes microtubules in mouse fibroblast cells

Taxol, a potent inhibitor of human HeLa and mouse fibroblast cell replication, blocked cells in the G2 and M phase of the cell cycle and stabilized cytoplasmic microtubules. The cytoplasmic microtubules of taxol-treated cells were visualized by transmission electron microscopy and indirect immunofluorescence microscopy. More than 90% of the cells treated with 10 micro M taxol for 22 hr at 37 degrees C displayed bundles of microtubules that appeared to radiate from a common site (or sites), in addition to their cytoplasmic microtubules. Untreated cells that were kept in the cold (4 degrees C) for 16 hr lost their microtubules, whereas cells that were pretreated with taxol for 22 hr at 37 degrees C continued to display their microtubules and bundles of microtubules in the cold. Taxol inhibited the migration behavior of fibroblast cells, but these cells did not lose their ability to produce mobile surface projections such as lamellipodia and filopodia.

Tubulin immunohistochemistry. Fixation methods affect the response of spinal cord cells in vitro

We report here the results observed when tubulin fluorescence immunohistochemistry is performed upon dissociated cultures of nervous tissue, principally of chick embryo spinal cord. When fixation includes nonpolar solvents or detergents, a uniform fluorescence is seen in neuron perikarya (with the exception of their nuclei), and the processes to which they give rise. Fixation with formaldehyde or glutaraldehyde alone, however, results in a discontinuous staining of neurites, and a less regular staining of their perikarya. The former pattern of response can be elicited if aldehyde fixation is followed by exposure to non-polar solvents. Such results are obtained both in thinly spread regions of the cultures, where neurons and their processes can easily be seen, and in the cell aggregates that also characterise them. Possible interpretations of these results are discussed.

Skin fibroblast microtubular network in Alzheimer disease

A preliminary observation from another laboratory recently suggested that a systemic microtubular defect may exist in Alzheimer disease. To investigate this hypothesis, we obtained skin biopsies from 4 patients with Alzheimer disease and 2 age-matched controls. Fibroblast cultures were established and the tubulin networks examined using immunoadsorbent purified antitubulin antibody and the indirect immunoperoxidase technique as well as electron microscopy. The cells were also examined after treatment with vinblastine and at senescence. The microtubular network appeared as delicate fibers radiating from the perinuclear region toward the cytoplasmic margins. No differences were recognized between the controls and the fibroblast cultures from patients with Alzheimer disease. Microtubules were not visualized following incubation with vinblastine, but positively staining intracytoplasmic paracrystalline inclusions were noted. No abnormalities of microtubules were recognized in the electron microscopic examinations. These findings suggest that the neurofibrillary neuronal degeneration of Alzheimer disease is not a manifestation of a systemic disorder of the microtubular network.

Smooth muscle autoantibodies and autoantigens

Smooth muscle autoantibody (SMA) was first found in the sera of patients with chronic active hepatitis and subsequently in the sera of patients with other autoimmune liver diseases, viral infections, certain cancers, heroin addicts and female infertility. SMA from patients with chronic active hepatitis reacts with many muscle and 'non-muscle' tissues while SMA from patients with other diseases usually reacts only with smooth muscle. These differences in immunofluorescent staining reactions suggest that SMA is a heterogeneous group of autoantibodies reactive with different smooth muscle autoantigens. As further evidence for this are findings that broad-reacting SMA can be absorbed out by actin, whereas autoantibodies reactive only with smooth muscle cannot, and that different SMAs give different immunofluorescent staining patterns using fibroblasts in tissue culture. Such staining patterns correspond to reactivity with either microfilaments, microtubules or intermediate filaments, ubiquitous cytoplasmic structures which make up the 'cytoskeleton'. Autoantibodies to actin-like microfilaments appear specific for chronic active hepatitis, autoantibodies to microtubules occur in infectious mononucleosis whereas autoantibodies to intermediate filaments occur in infectious hepatitis, chickenpox, measles and mumps. Predictably, future studies will show that presence of SMA with specificities for other proteins in the three types of cytoplasmic filaments, and given more information on antigenicity of the proteins and pathogenicity of the corresponding autoantibodies.

Relationship between movement and aggregation of centrioles in syncytia and formation of microtubule bundles

Previous reports from this laboratory have provided evidence suggesting that microtubules and 10-nm filaments serve both cytoskeletal and force-generating functions in the intracellular movement and positioning of nuclei in syncytia. It has been found that, during the process of cell fusion and nuclear migration in syncytia induced by the paramyxovirus simian virus 5, centrioles are transported in the cytoplasm and form large aggregates. These aggregates are usually found in regions adjacent to rows of aligned nuclei and large bundles of microtubules and 10-nm filaments. Colchicine prevents the translocation and aggregation of centrioles, but cytochalasin B has little effect on this process. These results suggest that the same cytoskeletal elements that are involved in nuclear migration and positioning--i.e., microtubules and 10-nm filaments--are also involved in the transport of centrioles. The possibility that aggregates of centrioles may serve as centers for the organization of microtubules and 10-nm filaments into the large bundles observed in the syncytia is discussed.

Quantitative reflection contrast microscopy of living cells

Mammalian cells in culture (BHK-21, PtK2, Friend, human flia, and glioma cells) have been observed by reflection contrast microscopy. Images of cells photographed at two different wavelengths (546 and 436 nm) or at two different angles of incidence allowed discrimination between reflected light and light that was both reflected and modulated by interference. Interference is involved when a change in reflected intensity (relative to glass/medium background reflected intensity) occurs on changing either the illumination wavelength or the reflection incidence angle. In cases where interference occurs, refractive indices can be determined at points where the optical path difference is known, by solving the given interference equation. Where cells are at least 50 nm distant from the glass substrate, intensities are also influenced by that distance as well as by the light's angle of incidence and wavelength. The reflected intensity at the glass/medium interface is used as a standard in calculating the refractive index of the cortical cytoplasm. Refractive indices were found to be higher (1.38--1.40) at points of focal contact, where stress fibers terminate, than in areas of close contact (1.354--1.368). In areas of the cortical cytoplasm, between focal contacts, not adherent to the glass substrate, refractive indices between 1.353 and 1.368 were found. This was thought to result from a microfilamentous network within the cortical cytoplasm. Intimate attachment of cells to their substrate is assumed to be characterized by a lack of an intermediate layer of culture medium.

Virus-specific and anticellular antibodies in molluscum contagiosum

Sera from patients with molluscum contagiosum showed a higher incidence of anticellular and fibrillar anticellular antibodies of IgM class as compared to sera from control subjects. Most patients with anticellular IgM antibodies also had molluscum contagiosum virus-specific antibodies. In a comparative study, there was a higher incidence of anticellular IgM antibodies to normal human epidermis and fibrillar anticellular IgM antibodies in molluscum contagiosum than in warts of psoriasis. The incidence in psoriasis was lower than warts and was similar to that found in control subjects.

Antitubulin agents enhance the stimulation of DNA synthesis by polypeptide growth factors in 3T3 mouse fibroblasts

Colchicine and other antitubulin agents markedly enhanced the stimulation of DNA synthesis by combinations of various growth factors such as epidermal growth factor, insulin, fibroblast-derived growth factor, and vasopressin in serum-free cultures of several quiescent 3T3 mouse fibroblast cell lines. Enhancing effects were observed based on continuous incorporation of [3H]thymidine into DNA as well as by autoradiographic labeling of cell nuclei. The concentration of colchicine and podophyllotoxin required to produce half-maximal enhancement of DNA synthesis stimulated by epidermal growth factor and insulin was 25-50 nM. Lumicolchicine did not produce enhancing effects. The disassembly of microtubules resulting from the action of colchicine, Colcemid, and vinblastine did not inhibit the stimulation of DNA synthesis in quiescent Swiss 3T3 fibroblasts by fetal bovine serum. We conclude that the cytoplasmic microtubule network in 3T3 mouse fibroblasts does not exert a positive regulatory function in the initiation of DNA synthesis but rather can produce a constraint on the initial action of the peptide growth factors in serum-free media.

Expression of microtubule networks in normal cells, transformed cells, and their hybrids

Microtubules play an important role in several cellular functions including cellular architecture and chromosome movement in cell division. Tubulin which polymerizes to form mictobules can be purified to homogeneity and used to raised antisera. Antisera prepared against porcine or chicken tubulin reacts well with mammalian tubulin. We have examined normal and transformed cells of mouse and human origin for microtubules by indirect immunofluorescence methods. Extensive networks of microtubules (MN) are easily detectable in normal and some transformed cells. The fixation procedure employed and the morphology and the cellular attachment properties seem to determine the ease of detection of MN in these cells. Cells derived from tumors and exhibiting several transformed phenotypes contained MN comparable to those of normal cells. Hybrids between transformed mouse cells and normal human cells were examined. They showed a variability in morphology, but all contained MN. These hybrids exhibited several transformed phenotypes. We conclude that in the cell lines we have examined there is no correlation between the transformed phenotypes and the organization of tubulin.

Organization of tubulin in normal and transformed rat kidney cells

We have carried out a quantitative biochemical and ultrastructural study of tubulin and microtubules in a normal rat kidney (NRK) cell line and its viral transformant (442) in culture. Under equivalent culture conditions, both cell lines contain the same amount of tubulin according to a colchicine-binding assay. The normal and transformed cells differ significantly, however, with respect to the state of organization of their tubulin. Counts of microtubules in sectioned cells indicate that NRK cells have almost twice as many microtubules per unit area of cytoplasm as the 442 cells. Centrifugation studies, on the other hand, show that 442 cells have almost twice as much pelletable tubulin as the NRK cells. We propose, therefore, that the transformed cells contain a large amount of tubulin which is in some alternative aggregate form that is not morphologically detectable as microtubles in the cytoplasm

Nerve fibers in culture and their interactions with non-neural cells visualized by immunofluorescence

Cultures of embryonic mouse spinal cord explants, alone or in combination with rat myotubes, were stained by indirect immunofluorescence using antibodies against three structural proteins to: (a) reveal the distribution of these proteins among different cell types, and (b) test the usefulness of antibody staining to reveal the gross morphology of the neurite network in complex cultures. Affinity column purified antibodies were used against chicken gizzard actin, porcine brain tubulin, and skeletal muscle alpha-actinin. Neurites were stained intensely by anti-actin as was the stress fiber pattern of underlying fibroblasts. With anti-tubulin, the staining of neurites was an order of magnitude more intense than the staining of the microtubule pattern of background fibroblasts. Neurite cell bodies and astrocyte-like glia cells were stained with anti-tubulin and their nuclei remained unstained. Anti-tubulin could thus be used to trace even the finest extensions of nerve processes in spinal cord and spinal cord-muscle cultures. Furthermore, it could be combined with the histochemical reaction for acetylcholinesterase (AChE, EC 3.1.1.7) to demonstrate AChE-positive neurons and specialized nerve-muscle contact sites. The staining of neural elements with anti-alpha-actinin was generally much weaker than with anti-actin and anti-tubulin. Neurites were stained only moderately in comparison to myotube Z lines in the same culture. However, a distinct staining of the periphery of dorsal root ganglion cells was observed. Thus, a protein immunologically related to muscle alpha-actinin is present in the nervous system. In myotubes, Z lines were stained intensely with anti-alpha-actinin while I bands were only faintly stained with anti-actin. In isolated myofibrils, both structures were stained intensely with the same antibody preparations.

Microtubules in mammalian heart muscle

Sections of adult mammalian cardiac muscles fixed at room temperature reveal numerous microtubules (24--28 nm in diameter) both near the nucleus and in the extra-myofibrillar space. Microtubules encircle the nucleus, are associated with the myofibrils in a helical arrangement, and form a network that runs transversely at the level of the I band and axially between the myofibrils. Microtubules are more numerous in muscle cells than previously recognized and may perform more than cytoskeletal function.

Localization of actin and microfilament-associated proteins in the microvilli and terminal web of the intestinal brush border by immunofluorescence microscopy

Indirect immunofluorescence microscopy was used to localize microfilament-associated proteins in the brush border of mouse intestinal epithelial cells. As expected, antibodies to actin decorated the microfilaments of the microvilli, giving rise to a very intense fluorescence. By contrast, antibodies to myosin, tropomyosin, filamin, and alpha-actinin did not decorate the microvilli. All these antibodies, however, decorated the terminal web region of the brush border. Myosin, tropomyosin, and alpha-actinin, although present throughout the terminal web, were found to be preferentially located around the periphery of the organelle. Therefore, two classes of microfilamentous structures can be documented in the brush border. First, the highly ordered microfilaments which make up the cores of the microvilli apparently lack the associated proteins. Second, seemingly less-ordered microfilaments are found in the terminal web, in which region the myosin, tropomyosin, filamin and alpha-actinin are located.

Requirement of calcium ions for cell degeneration with a toxin (vibriolysin) from Vibrio parahaemolyticus

A highly purified toxin (vibriolysin) from Vibrio parahaemolyticus caused degeneration of cell shape, such as bleb and balloon formation, of mouse myocardial cells and mouse melanoma cells in culture. An extracellular Ca2+ concentration of more than 10(-6) M was necessary for the degeneration of cell shape, but extracellular Mg2+, Na+, and K+ were not necessary. In the presence of extracellular Ca2+, vibriolysin also caused full contraction of myofibrils of mouse myocardial cells and reduction of both actin cables and tubulin networks of mouse melanoma cells. Vibriolysin also caused excess uptake of Ca2+ from the incubation medium by mouse myocardial cells and mouse melanoma cells. Chick myocardial cells, which show neither degeneration of cell shape nor full contraction of myofibrils, did not take up excess 45Ca2+ in the presence of vibriolysin. These findings suggest that the vibriolysin-induced degeneration of cell shape of mouse myocardial cells and mouse melanoma cells is due to excess uptake of Ca2+ from the incubation medium by the cells.

Double fluorescent staining for the separate demonstration of chromosomes and microtubules in mitotic cells in vitro

A simple fluorescent method for double staining of mitotic cells using a rhodamine B indirect immunofluorescent method for tubulin and the DNA-specific fluorescent dye Hoechst 33258 for nuclei and chromosomes is described. This procedure enables one through the use of appropriate excitation filters to view at will either chromosomes and nuclei or tubulin within the same cell.

The intracellular organization of actin and tubulin in cultured C-1300 mouse neuroblastoma cells (clone NB41A3)

Cells of clone NB41A3 of the C-1300 mouse neuroblastoma were grown to a critical density at which many of the cells flatten, assume a variety of shapes and sizes and some sprout processes resembling neurites. We have studied the distribution of actin and tubulin in these cells using fluorescence microscopy and antibodies against actin or tubulin under these conditions. Actin-containing structures are variably arranged and predominantly associated with motile areas of the cell periphery including the growth cone. Microtubules appear to run radially from the perinuclear area towards the cell periphery. When neurites are present, microtubules converge into them and run to the growth cone but rarely contact its edge.

Different intermediate-sized filaments distinguished by immunofluorescence microscopy

The major protein of intermediate-sized filaments in mouse 3T3 cells, for which the name vimentin is proposed, has a molecular weight of 57,000. Antibodies against vimentin and antibodies against prekeratin have been used in parallel in immunofluorescence microscopy on a variety of cultured cells as well as on frozen tissue sections. Both antibodies decorate extended wavy arrays of filaments that are different from microfilaments and microtubules. Intermediate filament bundles decorated by antibodies against prekeratin are predominant in many epithelial cells, including epithelia-derived tumor cells, and are not decorated by antibodies to vimentin. In contrast, intermediate filaments decorated by antibodies against vimentin are widespread among nonmuscle cells of mesenchymal origin, including transformed cells, and also occur in other cells. Perinuclear whorls of aggregates of intermediate filaments induced by prolonged treatment with Colcemid generally show strong decoration with antibodies against vimentin. No significant reaction with either antiserum has been observed in muscle structures or in brain nerve tissue. These observations show that intermediate filaments with similar ultrastructure and solubility characteristics can be distinguished immunologically.